Hereditary Diseases: Definition, Types & Treatments

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  • 0:04 Definition of Genetic…
  • 1:02 Types of Genetic Disorders
  • 3:20 Future Treatments for…
  • 4:17 Lesson Summary
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Lesson Transcript
Instructor: Rachel Torrens
People assume a disease came from your parents if it is called a genetic condition, but this isn't always true. In this lesson, the confusing term of 'genetic disorder' is clearly defined and future treatments for these conditions are also explored.

Definition of Genetic Disorders

Within minutes of a baby's birth, people start remarking about who this new little person resembles. 'Oh, he has his daddy's chin!' or 'She's got her mother's eyes!' but from where exactly do these similarities arise?

If you recall, every individual has 46 chromosomes, 23 chromosomes from each parent. The chromosomes are composed of deoxyribonucleic acid or DNA that is tightly bundled. Now, certain segments of the DNA which are responsible for different traits in an individual are termed genes. Thanks to the Human Genome Project, we now know that one chromosome has over 20,000 genes contained within it!

There is a lot of copying that has to take place to pass all these genes on from parents to a newly growing child. Understandably sometimes mistakes are made in the copying process. A genetic disorder is a condition resultant from abnormalities within an individual's genetic make-up.

Types of Genetic Diseases

There are four basic reasons for various genetic disorders:

  1. Abnormalities in the chromosomes
  2. Abnormalities in a single gene
  3. Abnormalities due to many factors
  4. Abnormalities due to teratogens

1. Abnormalities in the Chromosomes

Some disorders are the result of having too many or too few chromosomes. For example, Down Syndrome is a condition caused by having too many chromosomes. These disorders may be inherited from your parents, or they may occur spontaneously during DNA replication as the embryo grows.

2. Abnormalities in a Single Gene

In this instance, a specific gene from one or both parents leads to an abnormality. Examples of such a condition would be sickle cell anemia, cystic fibrosis, or hemophilia. These illnesses are inherited, a direct result from the parents' genetic make-up, and therefore are sometimes referred to as hereditary diseases.

3. Abnormalities Due to Many Factors

These conditions are caused either by problems in multiple genes or by many factors in addition to an abnormal gene. For example, heart defects and cleft palates are due to mutations in several genes. Examples of an illness caused by a genetic component and environmental factors would be cancer or coronary heart disease.

Let's look more closely at the example of breast cancer. Individuals with a BRCA gene mutation have a higher likelihood of developing breast cancer. However, other factors such as obesity, radiation exposure, or alcohol consumption also place an individual at increased risk for the development of breast cancer. Genetics can play a role in cancer development, but so can environmental factors.

4. Abnormalities Due to Teratogens

Finally certain substances, known as teratogens, can cause mutations in genes if a fetus is exposed to them while in utero. Alcohol, certain medications, and radiation exposure can lead to these types of genetic disorders. For example, a fetus exposed to copious amounts of alcohol can develop fetal alcohol syndrome. Likewise, a fetus exposed to phenytoin, a seizure medication, can develop a combination of birth defects known as fetal hydantoin syndrome.

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